The present invention relates to a shock mounting device for hot surface igniters and related methods and more particularly to a shock mount washer/ pad for silicon carbide hot surface igniters.
There are a number of appliances such as cooking ranges and clothes dryers and heating apparatuses such as boilers and furnaces in which a combustible material, such as a combustible hydrocarbon (e.g., propane, natural gas, oil) is mixed with air (i.e., oxygen) and continuously combusted within the appliance or heating apparatus so as to provide a continuous source of heat energy. This continuous source of heat energy is used for example to cook food, heat water to supply a source of running hot water and heat air or water to heat a structure such as a house.
Because this mixture of fuel and air (i.e., fuel/air mixture) does not self-ignite when mixed together, an ignition source must be provided to initiate the combustion process and to continue operating until the combustion process is self-sustaining. In the not too distant past, the ignition source was what was commonly referred to as a pilot light in which a very small quantity of the combustible material and air was mixed and continuously combusted even while the heating apparatus or appliance was not in operation. For a number of reasons, the use of a pilot light as an ignition source was done away with and an igniter used instead. An igniter is a device that creates the conditions required for ignition of the fuel/air mixture on demand, including piezoelectric igniters and silicon carbide hot surface igniters.
With hot surface igniters, such as the silicon carbide hot surface igniter, the heating tip or element is heated by electricity to the temperature required for the ignition of the fuel/air mixture, thus when the fuel/air mixture flows proximal to the igniter it is ignited. After a continuous combustion process is established, the electricity to the igniter element is typically turned off or discontinued. This process is repeated as and when needed to meet the particular operating requirements for the heating apparatus/appliance.
In use, it has been found that a percentage of heating apparatuses and appliances failed to operate or operate as intended because the igniters or the heating element thereof failed to generate the temperature required for ignition. Some of these failures occurred as a result of external loads, such as external impact loads, imposed on the igniter and/or igniter element during the manufacturing process, during shipping and handling, or during installation. While the impact loads were sufficient to fail the igniter or igniter element, such impact loads did not necessarily result in noticeable damage to the appliance or heating apparatus. Consequently, the failed igniter/igniter element typically remained undiscovered until after the appliance/heating apparatus had been installed and put to use.
The failures of the heating element typically manifested themselves as cracks in the element. These cracks, however, did not always manifest themselves as a complete crack through the element (i.e., through crack). Rather, in a number of cases the impact load caused the heating element to form a partial crack in the element. After a period of time, the cyclical heating of the element caused this partial crack to propagate until it caused the ignition element to essentially fail electrically (e.g., became a through crack or form an open). Consequently, the heating element functioned as intended for a period of time and then failed typically rendering the heating apparatus completely inoperable or rendering the appliance completely or partially inoperable. Tests by Applicants have shown that these partial cracks can lead to a failure over a wide range of times from a matter of minutes to hundreds of hours of operation.
Because a number of these igniter/heating element failures occurred during the warranty period for the appliance or heating apparatus, the manufacturer bore the cost for sending a repair person out to make a service call to determine the cause for the failure and to replace the failed igniter. Such service calls are expensive to the manufacturer and for a heating apparatus the service call can prove to be even more expensive because the service call usually cannot be delayed for a more convenient and less costly time. If the failure did not occur during the warranty period, then the service call was at the expense of the consumer. In addition to the expense, the failure of an appliance or heating apparatus irritates and annoys consumers because of the failure itself and because of the inconvenience of having to be available so the service person can make the service call. This irritation and annoyance can lead to the product getting a bad reputation for quality.
As such, the failures of igniters and/or the heating elements thereof is a particularly important concern of the manufacturer. Consequently, there is a continuing desire to reduce the number of failures and thereby reduce the number of warranty service calls and the annoyance to consumers. It thus would be desirable to provide a method and device that would make an igniter, in particular a hot surface igniter, more resistant to the external shock or impact loads that can occur during manufacturing, shipping and handling, and/or installation. It would be particularly desirable to provide such a device and method that would make an igniter more resistant to external shock or impact loads causing failure of prior art igniters. It also would be desirable to provide such a device that would be easy to install and that would not require a major modification to the mounting technique for the igniter or a change in the design of the appliance or heating apparatus. It also would be desirable to provide a heating apparatus or appliance that would be less costly for service repairs as compared to prior art heating apparatuses or appliances. The shock mounting device preferably would be simple in construction and the related methods would not require highly skilled users to install or utilize the device.
The present invention features methods and devices that reduce the external loads, in particular the external impact loads, that can be applied to an ignition device that is secured within a heating apparatus or an appliance. This ignition device is secured therein to a metal bracket or structural frame of the heating apparatus or appliance or it is secured to a burner tube provided therein. The external loads being particularly reduced are those being applied in one of the directions transverse to a long axis of a heating element of the ignition device.
In one aspect of the present invention there is featured a method for securing an ignition device to a support, which method includes disposing a shock mounting pad between a portion of the ignition device and a portion of the support. The shock mounting pad is configured and arranged so as to reduce external impact loads being applied to the ignition device as compared to the case where there is no shock mounting pad. In an exemplary embodiment, the external loads being reduced are those which would be applied to the ignition device, in particular the hearing element thereof, in one of the directions transverse to the long axis of a heating element.
The ignition device also is configurable so as to include a mounting mechanism (e.g., a mounting bracket) by which the ignition device is secured or attached to the support of the heating apparatus or appliance. In such a case the shock mounting pad is disposed between a portion of the mounting mechanism and at least a portion of the support.
Also featured is a method for improving the shock resistance of an ignition device to be attached to a support of a heating apparatus or an appliance. This method includes providing a shock mounting pad and securing the ignition device to the support such that the provided shock mounting pad is disposed between at least a portion of the ignition device and the support. The shock mounting pad being provided is configured and arranged so as to reduce external impact loads to the ignition device when it is secured to the support. As indicated above, the ignition device can further include a mounting mechanism and said securing can further include securing the mounting mechanism to the support such that the provided shock mounting pad is disposed between at least a portion of the mounting bracket and the support.
In another aspect of the present invention there is featured a shock mounting device for an ignition device secured to a support of a heating apparatus or an appliance. The shock mounting device includes a pad that is configured so as to be disposed between a surface of the support and at least a part of the ignition device. The pad also is configured and arranged so as to reduce communication of external impact loads, that could be applied, to the ignition device.
In particular embodiments, the above-described pad or shock mounting pad is generally made of a material having a thickness and firmness such that when the pad is disposed between an ignition device and the support it is secured to, the resultant structure is more resistant to external impact loads applied to the so-secured ignition device than the case where the ignition device is secured directly to the support without such a pad. The material comprising. the pad/shock-mounting pad also shall generally be any of a number of materials known in the art that are appropriate for the environment (e.g., temperature, pressure, humidity conditions) of the intended use as well as the intended function.
In more particular embodiments, the material, thickness and firmness of such a pad is selected so that the ignition device can resist an external load applied in one of a horizontal or vertical direction to a long axis of the heating element forming a part of the ignition device. In preferred embodiments, the material, thickness and firmness of such a pad also is selected so that the ignition device is capable of resisting an external impact load at least about 50 percent larger, more particularly a load at least about 2 times larger, and more specifically a load in the range of from about 1xc2xe to 3 times larger, on average than the average impact load that causes a failure of the ignition device without such a pad.
In specific embodiments, the pad has a thickness of at least about 0.030 inches, more specifically a thickness of at least about 0.0625 inches ({fraction (1/16)}), more particularly a thickness of about 0.125 inches (xe2x85x9) and further a thickness in the range of from about 0.030 inches to about 0.125 inches. The materials comprising the pad include, but are not limited to ceramic fibers, fiberglass, viton rubber, rubber, metal, foam plastics such as a silicone foam, for example, a Poron(copyright) silicone foam manufactured by the Rogers Corporation with or without an adhesive material applied thereto.
The above-described pad or shock mounting pad is formed into any of a number of geometric configurations known to those skilled in the art, that would be appropriate for a given application. Such configurations include, but are not limited to polygons (e.g., squares, rectangles, hexagons, octagons) and arcuate shapes (e.g., discs, circular wafers, washers). Such a pad can be arranged so as to also include one or more apertures so as to be capable of receiving in the aperture the securing device (e.g., nut, screw, rivet, stud) used to attach or secure the ignition device to the support. Such a pad also can be arranged so as to form a continuous surface which is to be pierced by the securing device. The above-described pad or shock mounting pad can further include an adhesive material (e.g., acrylic adhesive, silicone adhesive) applied to a surface of such a pad so the pad can be secured to one of the support or ignition device to facilitate the placement of the pad between the support and ignition device. In exemplary embodiments, the above-described pad or shock mounting pad is made from a ceramic fiber and is configured in the form of a washer having a xc2xd inch outer diameter, a xe2x85x9th inch diameter through aperture and a thickness in the range of from about 0.0625 to 0.125 inches.
Also featured is a heating apparatus or an appliance including such a shock mounting device according to the present invention that reduces the communication of loads to the ignition device thereof, which loads are external impact loads being applied to the heating apparatus or appliance.
Other aspects and embodiments of the invention are discussed below.